Postby Belton » August 29th, 2009 4:44 pm
You need to learn both.
What happened was this.
Japanese was a spoken language without a written form. So they imported Chinese characters and used them to represent the Japanese words. The kun readings.
However they also started using Chinese words (the dominant culture in the area, and also brought in with Buddhism), in the same way that English words are now absorbed into the language. This happened in about 3 phases which is why some words have multiple On readings.
However these readings aren't really Chinese, they are now wholly Japanese.
Kun-yomi and On-yomi are both used in Japanese.
The *tendency* is that compounds usually use On-yomi and single kanji words usually use Kun-yomi. (non-suru verbs, i adjectives, etc.)
How you learn them... I'd advise against trying to cram the readings of a given kanji. It's best to learn vocabulary that uses the readings. ie. learn in context. Mainly because it's hard to decide which particular reading to use in a given case unless you already know the word you are reading.